This invention relates generally to improved composite modified double base propellants suitable for use in end-burning missile motors which may be stored for long periods of time.
Solid propellants which are classified as composite modified double base (CMDB) propellants contain at least an oxidizer, fuel, binder, and plasticizer. Additional ingredients are added to modify the propellant ballistics or to give the propellant additional capabilities, e.g. long storage.
Impulse is the measure of the total energy of a missile motor. The delivered specific impulse is the impulse per pound of propellant and it is the most important parameter in propellant development. One common method of increasing the delivered specific impulse is to increase the propellants specific impulse efficiency which is defined as the ratio of the delivered specific impulse over the theoretical specific impulse.
It has been known that certain fluorine compounds have been helpful in increasing the delivered specific impulse of composite modified double base (CMDB) propellant. Unfortunately, the compounds used had a number of disadvantages. Fluorine-carbon compounds produced a stable and insensitive CMDB propellants, but they did not greatly increase the delivered specific impulse of the CMDB propellant. Fluorine-nitrogen and fluorine-oxygen compounds significantly increase the delivered specific impulse of the CMDB propellant but they also increased the instability and sensitivity of the solid propellant, thereby restricting the storage life and creating handling problems. Thus, no known fluorine containing compound has heretofore been discovered which would increase the specific impulse greatly without adversely affecting the composition in some other manner.
Another important parameter in propellant development is density. A greater density allows the design of smaller missiles or greater payloads or ranges for missiles. Unfortunately, it is also a difficult parameter to obtain because compounds which increase the density of the CMDB propellant also increase instability and sensitivity of the propellant.
Since most modern missile weapon systems require radar communication and tracking between a control station and an in-flight rocket for guidance control, any interference with the radar signal would hamper the guidance of the missile. Often the rocket exhaust plume is a substantial cause of this.
A significant contributor to the interference caused by the rocket exhaust plume is the chemical and thermal makeup of the exhaust plume. For this reason many propellant formulations are of limited value although they have a sufficiently high specific impulse. A good example of this type of propellant formulation would be those CMDB propellant using a large amount of aluminum for the metal fuel. Certain percentages of aluminum cannot be used although the resulting CMDB propellant would give a high specific impulse. Other percentages of aluminum can be used, but they present serious design problems.